1. Field of the Invention
The present invention relates, in general, to a fuel supply system of a vehicle and, more particularly, to a fuel supply system of a vehicle which improves the capability to cold-start an engine of a flexible fuel vehicle (FFV) which primarily uses ethanol in a normal condition, whereas it uses gasoline in a special condition such as cold starting of the engine at a low temperature.
2. Description of Related Art
Generally, a common fuel supply system of a flexible fuel vehicle (FFV), which primarily uses ethanol that is significantly cheaper than gasoline, requires a sub-tank 500 for storing gasoline, as shown in FIG. 1. In the FFV, in order to secure smooth starting of an engine at a low external air temperature of generally below 18° C., it uses gasoline stored in the sub-tank 500 to start the engine.
That is, ethanol has a substantially decreased vapor pressure relative to gasoline under the same temperature condition, so that at a low temperature such as in wintertime, the ethanol is difficult to be vaporized, making it difficult to start the engine. Thus, the fuel supply system is operated such that in a normal condition at a relatively high temperature, it supplies ethanol from a main tank 502, in which only ethanol is stored, to a main injector 504 so as to start the engine, whereas at a low temperature, it controls a solenoid valve 508 to supply gasoline stored in the sub-tank 500 to a cold-starting injector 506 so as to start the engine.
However, the supply system having the sub-fuel (e.g. gasoline) supply section needs a number of parts such as the sub-tank 500, a pump, the solenoid valve 508, a vent line connected with a canister, and the like, causing the manufacturing cost of a vehicle to increase. Further, since the supply system is generally installed in an engine compartment, there is a risk of fire occurring due to carelessness when supplying a vehicle with gasoline. Further, since the sub-tank 500 installed in the relatively narrow engine compartment has a relatively small storage capacity, the gasoline should be frequently supplied, causing inconvenience. Moreover, as expensive gasoline is used, the user's cost problematically increases.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.